1. Field of the Invention
The present invention relates to the field of compression ignition internal combustion engines.
2. Prior Art
Compression ignition engines are well known in the prior art. Such engines commonly known as diesel engines in which fuel (diesel or biodiesel) is injected into the combustion chamber after the heat of compression exceeds the self ignition temperature of the fuel, are to be distinguished from spark ignition engines wherein a fuel air mixture such as gasoline and air is compressed to below its self ignition temperature and then ignited. More recently, spark ignition of compressed natural gas (CNG) has been used in public transportation buses and the like. While such engine operation has its advantages, the current low cost of CNG being one of them, it suffers from the low volumetric energy content of the CNG, limiting the range of the vehicle.
CNG has also been used in compression ignition engines, with the ignition of the CNG being initiated by an injection of diesel fuel. This works, but also has its own disadvantages. At low power or idle, such engines run as diesel engines, at least in substantial part, thereby not taking full advantage of the low cost of CNG.